The present invention relates to a method and assembly for reducing the volume of a lung and, more particularly, to a mechanical lung volume reduction system comprising cords and anchors that pull on portions of a lung to compress the volume of a portion of the lung. The system may also supplement additional modes of lung volume reduction procedures which use occlusive plugs, valves, conduits, sleeves, etc.
The American Lung Association (ALA) estimates that nearly 16 million Americans suffer from chronic obstructive pulmonary disease (COPD) which includes diseases such as chronic bronchitis, emphysema, and some types of asthma. The ALA estimated that COPD was the fourth-ranking cause of death in the U.S. The ALA estimates that about 14 million and 2 million Americans suffer from emphysema and chronic bronchitis respectively.
Those inflicted with COPD face disabilities due to the limited pulmonary functions. Usually, individuals afflicted by COPD also face loss in muscle strength and an inability to perform common daily activities. Often, those patients desiring treatment for COPD seek a physician at a point where the disease is advanced. Since the damage to the lungs is irreversible, there is little hope of recovery. Most times, the physician cannot reverse the effects of the disease but can only offer treatment and advice to halt the progression of the disease. disease but can only offer treatment and advice to halt the progression of the disease.
The lungs deliver oxygen to the body and remove carbon dioxide. Healthy lung tissue includes a multitude of air passageways which lead to respiratory bronchioles within the lungs. These airways eventually lead to small sacs called alveoli, where the oxygen and carbon dioxide are exchanged through the ultra-thin walls of the alveoli. This occurs deep within the lungs, in an area which is accessed by a network of airways, consisting of a series of branching tubes which become narrower, shorter, and more numerous as they penetrate deeper into the lungs. As shown in FIG. 1, tiny air sacks called alveoli 1 surround both alveolar ducts 2 and respiratory bronchiole 3 throughout the lung. The alveoli are small, polyhedral recesses composed of a fibrillated connective tissue and surrounded by a few involuntary muscular and elastic fibers. These alveoli 1 inflate and deflate with air when we breathe. The alveoli are generally grouped together in a tightly packed configuration called an alveolar sac. The thin walls of the alveoli 1 perform gas exchange as we inhale and exhale.
During inhalation, as the diaphragm contracts and the ribs are raised, a vacuum is created in the chest, and air is drawn into the lungs. As the diaphragm relaxes, normal lungs act like a stretched balloon and rebound to the normal relaxed state, forcing air out of the lungs. The elasticity of the lungs is maintained by the supportive structure of the alveoli. This network of alveoli provides strength to the airway walls, as well as elasticity to the lungs, both of which contribute to the lung's ability to function effectively.
Patients with pulmonary disease have reduced lung capacity and efficiency due to the breakdown of lung tissue. This often is caused by smoking. In cases of severe chronic pulmonary disease, such as emphysema, lung tissue is destroyed, reducing the strength of the airways. This reduction and strength of the airway walls allows the walls to become “floppy” thereby losing their ability to remain open during exhalation. In the lungs of an emphysema patient, illustrated in FIG. 2, the walls between adjacent alveoli within the alveolar sac deteriorate. This wall deterioration is accelerated by the chemicals in smoke which affect the production of mucus in the lungs. Although the break down of the walls of the alveoli in the lungs occurs over time even in a healthy patient, this deterioration is greatly accelerated in a smoker causing the smoker's lungs to have multiple large spaces 4 with few connecting walls in the place of the much smaller and more dense alveoli spaces 1 in healthy lung tissue.
A cross section of a diseased emphysematous lung will look like Swiss cheese due to the deterioration of the alveoli walls which leaves large spaces in the tissue. In contrast, a cross section of healthy lung tissue has few or no noticeable holes because of the small size of the alveoli. When many of the walls of the alveoli 1 deteriorate, as shown in FIG. 2, the lung has larger open spaces 4 and a larger overall volume, but has less wall tissue to achieve gas exchange.
In this diseased state, patients suffer from the inability to get the air out of their lungs due to the collapse of the airways during exhalation. As a result, heavily diseased areas of the lung become over-inflated with the air that cannot escape due to the collapse of the airways. This air remains in the lung and is non-functional as it does not aid in the blood-gas exchange process. Because the lungs are limited to the confines of the chest cavity, this over-inflation restricts the in-flow of fresh air and hampers the proper function of healthier tissue. As a result of the over-inflation, patients experience significant breathlessness. Thus, the emphysema patient must take in a greater volume of air to achieve the same amount of gas exchange as a healthy individual. However, individuals suffering from emphysema still have insufficient gas exchange even when they take in as much air as their chest cavity can accommodate. Emphysema patients will often look barrel-chested and their shoulders will elevate as they strain to make room for their over-inflated lungs to work.
Emphysema is characterized by irreversible biochemical destruction of the alveolar walls that contain the elastic fibers, called elastin, described above. The destruction of the alveolar walls results in a dual problem of reduction of elastic recoil and the loss of tethering of the airways. Unfortunately for the individual suffering from emphysema, these two problems combine to result in extreme hyperinflation (air trapping) of the lung and an inability of the person to exhale. In this situation, the individual will be debilitated since the lungs are unable to perform gas exchange at a satisfactory rate.
One further aspect of the alveolar wall destruction that is associated with emphysema is that the airflow between neighboring air sacs, known as collateral ventilation or collateral air flow, is markedly increased as when compared to a healthy lung. While alveolar wall destruction decreases resistance to collateral ventilation, the resulting increased collateral ventilation does not benefit the individual since air is still unable to flow into and out of the lungs. Hence, because this trapped air is rich in CO2, it is of little or no benefit to the individual.
In cases of severe emphysema, lung volume reduction surgery (LVRS) improves lung efficiency of the patient and allows the patient to regain mobility. In lung volume reduction surgery, a diseased portion of an emphysematous lung having a large amount of alveolar wall deterioration is surgically removed as illustrated in FIG. 3. LVRS is performed by opening the chest cavity, retracting the ribs, stapling off, and removing the more diseased portion of the lung 31. This allows the remaining healthier lung tissue to inflate more fully and take greater advantage of the body's ability to inhale and exhale. Since there is more inspired air there is increased gas exchange in the healthier portion of the lung. As a result lung efficiency improves.
Lung volume reduction surgery is an extremely invasive procedure requiring the surgical opening of the chest cavity and removal of lung tissue. This surgery has substantial risks of serious post-operative complications, such as pneumothorax, and also requires an extended convalescence.
Accordingly, it is desirable to achieve the benefits of improved air exchange for emphysema patients provided by LVRS without invasive open chest surgery and the associated complications.
More recently, means to reduce lung volume have been discussed which includes occlusive plugs, one-way valves, sleeves over an emphysematous portion of lung, and “airway bypass” (the creation of passages between airways and lung parenchyma). These methods attempt to reduce lung volume by drawing portions of the lung then placing an implant (such as a plug or valve) inside the airway, or by inserting a sleeve over the collapsed portion of the lung to maintain the reduction in volume. These approaches are described below. However, in some cases collateral ventilation between the air sacs may cause difficulties when attempting to maintain a reduction of lung volume. Accordingly, use of the anchoring system of the present invention may assist in either permanently or temporarily reducing the volume of at least a portion of the lung to supplement the variously described means.